build: Use jacoco 0.8.7 for compatibility with Kotlin 1.5

Signed-off-by: Álvaro Brey Vilas <alvaro.brey@nextcloud.com>

build.gradle

@@ -461,3 +461,7 @@ detekt {
 shot {
     showOnlyFailingTestsInReports = ciBuild
 }
+
+jacoco {
+    toolVersion = "0.8.7"
+}